Barrel rifling means



E. B. F. SCHNECK BARREL RIFLING MEANS Sept. 23, 1941.

Filed June 3; 1940" INVENTOR. jmkfllSc/meck MM); ATTORNEY.

Patented Sept. 23, 1941 UNlTED' STATES PATENT OFFICE 2 1m momma I it Edwin n. r. Schneck,,Detroit, such.

Application June 3, 1940, Serial No. 338,469

6 Claims. (Cl. 90-28-1) portions. The projectile which is used with this type of barrel has circumferential vane-like portions, which fit the relatively larger diameter of the breech portion, and as the projectile passes through the bore the vane-like formations collapse radially inwardly to enable the projectile to pass through the small diameter muzzle portion. .The purpose of the vanes is to increase the pressure area of the projectile for the attainment of higher projectile velocities.

Due to the varying diameter of the bore, rifle grooves cannot be formed by ordinary broaching methods, and an important object of this invenhaving a bore 2 therein. The bore 2 has a breech portion a of uniform diameter, a muzzle portion b also of uniform diameter, but of a diameter smaller than the breech portion, and a tapered portion c connecting the breech and muzzle portions. The projectile used with this type of barrel is shown at 3,,and as illustrated, has circumferential vane-like formations 4 of a diameter corresponding to the diameter of the breech portion. These vane-like formations collapse radially inwardly as the projectile passes through the bore.

Formation of rifle grooves in the bore 2 presents a problem due to its varying diameter, and the means hereinafter described is designed for this particular purpose. Although designed for this particular purpose, however, it will be undertion is to provide means including broach-like cutters and guide means-therefor which functions to guide the cutters in a spiral path through the bore so that they cut a spiral groove in the wall of the bore, of uniform depth throughout the length of the bore. To this end, the invention provides a body having an external shape substantially identical to the shape of the bore. On this body is formed a spiral track (or possibly a multiplicity of tracks), and the broach .like cutters are adapted to travel in this track while the body is held stationary in the bore. As thecutters are drawn or otherwise caused to .move through the track they cut a spiral groove in-the surface'of the bore.

Other objects and advantages will become more fully apparent as reference is had to the accompanying drawing wherein the-invention is illustrated, and in which Fig. 1 is a fragmental longitudinal cross section of a firearm barrel having a tapered bore,

Fig. 2 is a fragmental elevation of a cutter uid Fig. 3 is a fragmental elevation of a second cutter guide,

Fig. 4 is a section illustrating the cutters,

Fig. 5 is a plan of the cutters,

Fig. 6 is a transverse section illustrating a cutter. in the guide track, and

Fig. 7 is a section illustrating an alternative formation of the guide tracks.

In Fig. 1 there is illustrated a firearm barrel stood that it is capable of other applications such, for example, as in the case of abore having a uniform diameter.

In Fig. 2 there is illustrated a body 5 of a shape and size such that it is capable of fitting accurately within the bore 2. The surface of the body 5 is formed with a spiral groove track 6 adapted to receive cutters I, as shown in Figs. 4 and 5. To cut a spiral groove in the surfac of the bore 2, the roove track while the body 5 is held in the bore. The cutters l comprise a multiplicity of hlngedly connected bodies each having a cutting edge la. The cutting edges 1a vary in height as between different bodies, after the manner of broach cutters, so that as the cutters pass through the bore the first cutter takes a shallow cut, the second a little deeper, and so on until the final cutter takes the final cut. The portions 1b of the cutters, as may be seen in Fig. 6, are shaped to engage the surface of the bore being grooved, laterally of the grooves, for maintaining the cutter bodies I fiat within the groove track. These cutters may, for example, be pulled along the groove by a flexible wire-like element Ill.

The groove track 6 is shown in Fig. 6 as having straight side walls, but they may be undercut, as ilustrated at 8 in Fig. 7 for the reception of cutters having dovetail portions. Fig. 7 also 11- lustrates the provision of a multiplicity of groove tracks on the body 9, and it will be understood from this disclosure that 6 may likewise be provided on the body 5.

When a single groove body 5 is rotated a predetermined number of deas to form a multlplicitypf parallel spiral grooves I in the wall. of the bore 2. Due to the varying cutters 1 are moved through the a multiplicity of grooves 1 track 6 is employed, the

diameter of the bore the grooves so formed will have a larger land therebetween at the larger end of the bore than at the smaller end of the bore. For this reason a second body 5a is provided, of a shape and size identical to'the shape and size of the 'body i, and having a groove track 6a therein. At the larger diameter end of the body- 511 the groove 61': is slightly offset from the position of the groove 6, whichis illustrated on the body 5a by broken lines for purposes of comparison. As the groove 6a extends toward the smaller end of the body 5a it gradually approaches the position of the groove 6, and at the smaller end of the body it exactly overlies the position of the groove 6. J

The bodyv 5a is placed in the bore 2 in positions. corresponding to the positions in which the body 5 was previously placed, and cutters are passed through the bore in each of the successive positions. In this manner spiral grooves are formed which are of greater width at the larger end of the bore than at the smaller end, thus making it possible to provide grooves-and lands of equal width at every cross section of the barrel.

Although a speciflc embodiment of the invention has been illustrated and described, it will be understood that various changes may be made within the scope of the appended claims without departing from the spirit of the invention, and such changes are contemplated.

What is claimed is: I

1. Means for cutting a rifle groove in the wall of a bore, comprising a body having a shape and size such that it fits snugly within the bore, said body having at least one spiral groove in the surface thereof, and a cutter received in said groove track and adapted to move therethrough with respect to said bore and said body while said body is held in the bore.

2. Means for cutting a rifle groove in the wall of a bore, comprising a body having a shape and size such that it fits snugly within the bore, said body having at least one spiral groove in the surface thereof, and a multiplicity of cutters connected in a series, said cutters being .received in said groove track and being adapted to move therethrough with respect to said bore and said adapted to move therethrough with respect to said bore and said body while the body is held in the bore.

4. Means for cutting a rifie groove in a firearm barrel bore having a breech portion of larger iameter than its muzzle portion and a tapered portion connecting thebreech and muzzle portions, comprising a body having a shape and size such that it snugly fits within the different diameter portions of the bore, said body having at least one spiral groove track in the surface thereof, a

multiplicity of cutters connected in a series, said cutters, being received in said spiral groove track,

said cutters being adapted to be moved through said groove track while the body is in the bore, and each trailing cutter being adapted to cut the wall of the bore to a greater depth than the-cutter body while the body is held in the bore, each trailing cutter of the series being adapted to cut the wall of the bore to a greater depth than the cutter whichit follows.

3. Means for cutting a rifle groove in a firearm barrel bore having a breech portion of larger,

diameter than its muzzle portion and a tapered portion connecting the breech and muzzle porwhich it follows.

5. Means for cutting a rifle groove in a tapered bore, comprising a-cutter-adapted to be moved through the bore, means for guiding said cutter in a spiral path which tapers at a rate corresponding to the taper of the bore as the cutter is passed through the bore, and a second guide means for guiding said cutter in a subsequent.

pass and through a spiral path which tapers at a rate corresponding to the taper of the bore and which is slightly ofiset from the first path at the larger end of the bore, the amount of oifset of the second path decreasing as the diameter of the bore decreases.

6. Means for cutting a rifle groove in a firearm barrel bore having a breech portion of larger diameter than its muzzle portion and a tapered portion connecting the breech and muzzle portions, comprising a cutter adapted for movement through the bore, means for guiding said cutter in a spiral path which tapers at a rate corresponding to the taper of'the tapered portion as said cutter passes through the bore, and a second the first path in the muzzle portion.

EDWIN B. F. SCHNECK. 

